Effects of lesions to amygdala, ventral subiculum, medial prefrontal cortex, and nucleus accumbens on the reaction to novelty: Implication for limbic—striatal interactions.

Abstract

The effects of bilateral excitotoxic lesions of 3 major sources of afferents to the ventral striatum (nucleus accumbens) were compared on an open field test of food neophobia allowing the choice between familiar and novel food. Whereas lesions of the basolatera] amygdala and ventral subiculum had qualitatively similar effects to reduce food neophobia (although not affecting the latency to eat), amygdala lesions increased and the ventral subiculum decreased locomotor activity. In contrast, damage to the ventromedial prelimbic prefrontal cortex only affected initial food choice and latency' measures. By comparison, excitotoxic lesions of the nucleus accumbens itself and intra-accumbens infusion of the TV-methyl-D-aspartate (NMDA) receptor antagonist APS increased activity and attenuated food neophobia. Results are discussed in terms of the role of limbic and prefrontal neuronal networks converging in the nucleus accumbens to control different aspects of the behavioral response to novelty.It is now apparent that the functioning of the ventral striatum, including the nucleus accumbens (n. accumbens), is determined by its so-called limbic afferents from the amygdala, hippocampal formation, and prelimbic corlex. Mogcnson (1984) investigated functional interactions between the limbic system and the striatum using a combined electrophysiological and behavioral approach that focused on the control of locomotor activity by output of the n. accumbens, controlled in turn by its limbic input and modulated by the ascending mesolimbic dopamine system. This approach arose from two distinct lines of work: one demonstrating a special role for the n. accumbens in the control of spontaneous and drug-induced locomotor activity, and the other characterizing the role of the limbic system in mediating behavioral and aversive responses to novelty, including aversion and exploration. Thus, dopaminedependent mechanisms of the n. accumbens mediate the locomotor stimulant effect of amphetamine in the rat

Differential behavioral profile induced by the injection of dipotassium chlorazepate within brain areas that project to the nucleus accumbens septi

“…All these present evidences allow us to think that present findings could be correlated with previously described circuitries interactions, like those described for AMY and PFC circuitries [9], AMY and NAS [11], and AMY, PFC, Hip and NAS [28,29,49,50,52]. Like it was previously said, an activation of AMY, Hip and some zones of PFC has been correlated with stress arousal and its correlative anxiety [63].…”

“…In this previous study in rats, more stressing situations (plus maze and footshocks) activated PFC, AMY and NAS, and lower stressors (air puff) did not activate NAS foslike activity, suggesting a necessary degree of stress to activate it [18]. The interactions between limbic and striatal structures has been described and mainly related to pathways from AMY to NAS [11]. However, as it was previously suggested [9], other pathways connecting the involved areas could be acting in these processes [8,35,36] and cannot be excluded.…”

Learning capabilities enhanced in harsh environments: a common garden approach

“…This possibility, in particular, may explain the differences in response to novelty. It is possible that exposure to corticosterone during development may produce a response in specific brain regions such as the amygdala, which may affect neophobia responses (Burns et al 1996). However, we argue that these maternal effects, should they exist, are likely to be the result of selection as well.…”

Paradoxical Hormonal and Behavioral Responses to Hypothyroid and Hyperthyroid States in the Wistar–Kyoto Rat

“…TR␤ 2 has also been found in different brain regions (Li and Boyages 1996). However, little is known of the effect of thyroid hormone milieu on TR expression in brain regions that have been suggested to be involved in the OFT or FST behavior; namely, the amygdala (Werka et al 1978;Shimazoe et al 1988;Nieminen et al 1992) and the prefrontal cortex (Burns et al 1996;Zangen et al 1999). Thus, distribution of the TR isoforms and their regionspecific response to changes in thyroid hormone milieu could be responsible for the differential effects of thyroid hormones on behavioral measures in the OFT and the FST, such as decreased activity (swimming) in the Wistars in the FST but increased activity (segments entered) in the OFT in response to hyperthyroid states.…”